I did it with my Palm Pre. After a couple hours on a Friday I got it to work. It was beautiful all weekend. Then on Monday I got a request for an online update, so I said sure. They slammed the door on that free tether. It was scary doing it with warning after warning of bricking your phone.
I'll be getting the Sprint Android version 4G on Sept 1 when I am eligible for an upgrade. Not sure which phone to take. New phone has 3D camera. Not sure if its worth extra cost.